Impact of temperature and flow rate on oxygen dynamics and water quality in major Turkish rivers

This study investigates the effects of temperature and flow variations on dissolved oxygen and biochemical oxygen demand across four major Turkish rivers: Kızılırmak, Sakarya, Seyhan, and Yeşilırmak. An Extended Streeter-Phelps Model, incorporating temperature-dependent deoxygenation and flow-sensitive reoxygenation rates, was employed to simulate oxygen dynamics under diverse environmental condition. Results indicate that increased temperature generally reduces oxygen levels due to lower solubility, while biochemical demand initially rises, reflecting accelerated organic decomposition. Higher flow rates, however, help sustain oxygen levels by enhancing mixing and dilution. Each river exhibited unique responses to these factors, influenced by its hydrological and anthropogenic characteristics. The model demonstrated strong predictive accuracy, with R² values ranging from 0.80 to 0.95 and RMSE values generally below 5.5, effectively capturing complex interactions that traditional models often overlook. These findings underscore the importance of managing flow and temperature impacts on river ecosystems, particularly under seasonal and human-induced pressures. This study provides valuable insights for water quality management and conservation strategies, emphasizing the utility of dynamic modeling frameworks in diverse river systems.